Recovery and the Quality of Gypsum from Natural and Artificial Pans of Various Salt-Ponds of Kanyakumari and Tuticorin Districts, Tamilnadu, India

The story of the salt is the story of mankind. Salt has played a vital role in the development of man's activities, trade, politics, culture and world's economy from pre-historic time. The most abundant source of common salt (NaCl) is sea water, in view of that 71% of earth surface is covered with sea water, which contains 2.5% common salt. Next to sea water the concentration of sodium chloride is high in subsoil brine and backwater brine. The production of common salt is mainly by solar evaporation of sea brine, subsoil and backwater brines. Thus the technique of solar salt production involves fractional crystallization of the salts in different brines. While the process for solar evaporation of brines is same around the world, but the product quality vary considerably. During the production of salt, the valuable by-product of gypsum (CaSO₄.2H₂O) is also obtained. The sea water contains about 3.6% CaSO₄, which is in-exhaustible and can be renewable. The recovery of gypsum from different brines is substantial and its comparable with the production of commercially available mineral gypsum in market. The most influential parameters potentially affecting the crystallization process of gypsum were water, salinity, temperature, type and amount of dissolved organic compounds, PH and organic waste products from microorganisms. The quality of gypsum from natural and artificial pans in the salt ponds of Kanyakumari and Tuticorin districts were taken in to consideration.